| 摘要 |
A low-power stop mode "snooze" timer is implemented in the processing unit of a communication system, which runs without the use of the usual crystal-controlled oscillator. The "snooze" timer is implemented by a second oscillator with associated timer circuit. The second oscillator runs continually and feeds a timer which is loaded with a suitable value. The timer, when timed out or expired, will reactivate the main processing functions, thus allowing the successful reception of an external signal from a remote transmission source. To compensate for the inaccuracy of the second oscillator due to its dependence upon voltage, process and temperature, the snooze timer's output is calibrated during the wake-up periods against a timing signal derived from the internal crystal-controlled timing source. This calibration compensates for the inherent frequency instability of the second oscillator and allows a timing signal of sufficient accuracy to be maintained over the stop cycle. |
